Field of the Invention
The present disclosure relates to an ink, an ink stored container, an inkjet printing method, and an inkjet printing device.
Description of the Related Art
Compared with other printing methods, inkjet printing methods have advantages that the methods have simple processes, can be easily accommodated to full-color operations, and can provide high-resolution images even when used on apparatuses having simple configurations. These advantages are spreading the inkjet printing methods to personal and office use and commercial printing and industrial printing fields. In the inkjet printing methods, water-based ink compositions using a water-soluble dye as a coloring material are mainly used. However, the water-based ink compositions have disadvantages of being poor in water resistance and light resistance. Hence, pigment inks using a water-insoluble pigment instead of a water-soluble dye are being developed.
For acceleration of a drying speed of an ink attached on a print medium as a measure for promoting high-speed printing, a means is taken to add a permeating agent such as a hydrophobic solvent in an ink to make water permeate a print medium and accelerate drying.
Hence, there is a need that dispersion stability of a pigment be satisfied in both of the following environments: a pigment dispersion in a water solvent; and an ink in a hydrophobic solvent.
If dispersion stability in a hydrophobic solvent is poor, pigment particles may aggregate and clog nozzle holes of an inkjet head to constitute a factor of no discharging.
Unlike water-based dye inks prepared by dissolving a dye in water, water-based pigment inks used in the inkjet printing methods or as writing materials have a need that the pigment that is insoluble in water be dispersed in water stably for a long term. Therefore, various pigment dispersants are being developed. For example, there is proposed a graft polymer including an aromatic ring in a side chain. It is said that use of this graft polymer as a pigment dispersant has ensured an ink storage stability at 70° C. for 3 days (see, e.g., Unexamined Japanese Patent Application Publication No. 2011-105866).